Patterns of tuberculosis risk over time among recent immigrants to Ontario, Canada

SETTING: Canada receives more than 200000 immigrants annually. Immigrants account for 92% of tuberculosis (TB) cases in Toronto, Ontario. Epidemiological profiling of recent immigrants is needed to provide more effective TB programs. DESIGN: A population-based, retrospective cohort study of recent immigrants to Ontario, 1990-1997. We generated adjusted rates, risk ratios (RRs), hazard rates since arrival, and a complementary log-log model to describe TB risk, compare the survival distributions between different sexes, age groups and world regions of birth, and determine predictors of disease. RESULTS: TB in recent immigrants was 23 times (95%CI 20.9-25.5) higher than in Canadian-born, non-aboriginal people. Those aged 16-30 and > 65 years experienced the highest rates. Sub-Saharan Africa had the highest rates for both sexes (RR 95.5, 95%CI 84.3-108.2), followed by India and Asia. Hazard rates decreased after arrival, but remained elevated. The highest risk was associated with arrival in 1990 and living in Canada < 1 year. CONCLUSION: Risk for TB varied by region of birth, age at landing and time since arrival. Sex was not significant. Persons from sub-Saharan Africa and age > 65 years were the highest risk groups. Risk decreased significantly in the first 1-2 years after arrival, after which it plateaued.